Attempt to avoid some of the Enoent issues

app/models/asset.rb

@@ -76,7 +76,7 @@ class Asset
 
   mount_uploader :file, AssetUploader
 
-  before_save :store_metadata, unless: :uploaded?
+  before_save :store_metadata, unless: :uploaded?, if: -> { changes.include?(:file) }
   after_save :schedule_virus_scan
   after_save :update_indirect_replacements_on_publish
   after_save :backpropagate_replacement

app/workers/virus_scan_worker.rb

@@ -9,7 +9,12 @@ def perform(asset_id)
       begin
         Rails.logger.info("#{asset_id} - VirusScanWorker#perform - Virus scan started")
         Services.virus_scanner.scan(asset.file.path)
-        asset.scanned_clean!
+        # This is to deal with a concurrency issue in production
+        # It looks like sometimes VirusScannerWorker can be scheduled several times for one file
+        # And the other process might change the state already of as the virus scan take time
+        # This if condition is to avoid unnecessary state transitions and therefore other
+        # concurrency issues
+        asset.scanned_clean! if Asset.find(asset_id).unscanned?
       rescue VirusScanner::InfectedFile => e
         GovukError.notify(e, extra: { id: asset.id, filename: asset.filename })
         asset.scanned_infected!

spec/workers/virus_scan_worker_spec.rb

@@ -39,6 +39,18 @@
     end
   end
 
+  context "when the asset becomes marked clean by another process" do
+    it "does change the asset state" do
+      allow(scanner).to receive(:scan) do
+        asset.scanned_infected!
+      end
+
+      worker.perform(asset.id)
+
+      expect(asset.reload).not_to be_clean
+    end
+  end
+
   context "when the asset is already marked as infected" do
     let(:asset) { FactoryBot.create(:infected_asset) }